Graphics Programs Reference
In-Depth Information
return headerView;
}
You don't have to specify the suffix of the file name;
NSBundle
will figure it out. Also,
notice that you passed
self
as the owner of the XIB file. This places the instance of
ItemsViewController
in the
File's Owner
hole of the XIB file.
The first time the
headerView
message is sent to the
ItemsViewController
, it
will load
HeaderView.xib
and keep a pointer to the view object in the instance vari-
able
headerView
. The buttons in this view will send messages to the
Item-
sViewController
when tapped.
Now that you've created
headerView
, you need to make it the header view of the table.
This requires implementing two methods from the
UITableViewDelegate
protocol
in
ItemsViewController.m
.
- (UIView *)tableView:(UITableView *)tv viewForHeaderInSection:(NSInteger)sec
{
return [self headerView];
}
- (CGFloat)tableView:(UITableView *)tv heightForHeaderInSection:(NSInteger)sec
{
// The height of the header view should be determined from the height of the
// view in the XIB file
return [[self headerView] bounds].size.height;
}
These two methods are listed as optional in the protocol, but if you want a header view,
you must implement both.
Now that these methods are implemented, the
UITableView
will send these messages
to its
delegate
, the
ItemsViewController
, when it needs to show the header
view. The first time
tableView:heightForHeaderInSection:
is sent to
Item-
sViewController
, it will send itself the message
headerView
. At this time,
headerView
will be
nil
, which will cause
headerView
to be loaded from the XIB
file.
Build and run the application to see the interface. Ignore the incomplete implementation
warnings; you'll implement
toggleEditingMode:
and
addNewItem:
shortly. Until
you do, tapping a button will generate an exception because the action methods of the but-
tons are not implemented.
